Conventionally, memory devices including resistance change storage elements each to store one of a plurality of, typically four or more, resistance states as data represented in two or more bits (multi-valued data) are known. For example, in reading data in these memory devices, the sensing operation of comparing the voltage when reading after applying a predetermined voltage (read voltage) to a bit line connected to a selected storage element and a reference voltage corresponding to one of a plurality of threshold resistances is repeated while changing the reference voltage so as to identify the resistance state of that storage element.